This invention relates generally to refrigeration systems and equipment, and more particularly concerns a refrigeration system for a soft drink bottling plant which is capable of producing significant electric power savings by fully utilizing all of the cooling capacity available in the system and under predetermined conditions removing cooling capacity which is not needed.
In a soft drink plant, the soft drink is constituted by mixing soft drink syrup with water and carbon dioxide (CO.sub.2) gas at low temperatures in a beverage cooler/carbonator. The beverage cooler/carbonator is a pressure vessel that is charged with about two atmospheres of CO.sub.2 gas. One type of cooler/carbonator has a baudelot corrugated cooling plate over which the mixture of water and syrup flows from top to bottom. As a film of the mixture of water and syrup descends over the cooling plate, the mixture is cooled to approximately 34.degree. F. so that the mixture can absorb sufficient CO.sub.2 gas to assure that the resulting soft drink beverage has the right volume of carbonation.
In order to assure quality in the production of soft drinks, the cooling plate in the cooler/carbonator must remain at a constant temperature (about 30.degree. F.) during the carbonation of the syrup and water mixture. Any variations in temperature in the cooler/carbonator may result in inadequate carbonation of the beverage.
The cooling plates are evaporators having an inlet connected to a high pressure liquid refrigerant line and an outlet connected to a refrigeration suction line. The temperature of the cooling plate of the cooler/carbonator is directly related to the pressure at the suction line side of the cooling plate. The suction pressure is established by a constant pressure regulator valve, but the compressor unit connected to the suction line must be able to provide sufficiently low suction pressure to assure that there will be an adequate pressure drop across the regulator valve.
In a typical soft drink plant there may be several cooler/carbonators all connected to a single high pressure liquid refrigerant manifold and to a single refrigeration suction manifold and each having its own regulator valve. Also in a typical soft drink plant refrigeration capacity is provided by a bank of individually controllable compressor units connected to a single high pressure discharge manifold and the single suction manifold which compressor units can be turned on or shut off individually to increase or decrease refrigeration capacity as required.
During production, the cooler/carbonators cycle on and off due to interruptions or delays in the production line. If, for example, a cooler/carbonator is shut off because of an interruption in production, the compressor units continue to provide refrigeration capacity which is essentially wasted until the cooler/carbonator can be restarted. In prior art systems, false loading is often provided so that the refrigerant vapor is simply passed through a closed loop while the cooler/carbonator is shut off. Because on restart the cooler/carbonator requires full refrigeration capacity, compressor units cannot be shut off, or the refrigeration capacity will be insufficient when the cooler/carbonator restarts.
Moreover, to ensure a constant, ripple free temperature (suction pressure) in the cooler/carbonators even while normal uninterrupted production is proceeding, a certain percentage of overcapacity is required so that variations in incoming water temperature will not create a pressure ripple at the suction side of the cooling plates resulting in temperature ripple in the cooler/carbonators.